U.S. patent application number 10/256672 was filed with the patent office on 2004-04-01 for system and method for cleaning in-process sensors.
Invention is credited to Cronin, James Timothy, Elkins, Thomas Shields, Helberg, Lisa Edith, Strzelecki, Angela Ruth.
Application Number | 20040060576 10/256672 |
Document ID | / |
Family ID | 31977871 |
Filed Date | 2004-04-01 |
United States Patent
Application |
20040060576 |
Kind Code |
A1 |
Cronin, James Timothy ; et
al. |
April 1, 2004 |
System and method for cleaning in-process sensors
Abstract
A cleaning system and method for in-process sensors wherein a
scouring jet discharges process fluid as the cleaning agent to
remove solids and other contaminants from the surface of the
sensor.
Inventors: |
Cronin, James Timothy;
(Townsend, DE) ; Elkins, Thomas Shields; (Waverly,
TN) ; Helberg, Lisa Edith; (Middletown, DE) ;
Strzelecki, Angela Ruth; (Boothwyn, PA) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY
LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
31977871 |
Appl. No.: |
10/256672 |
Filed: |
September 27, 2002 |
Current U.S.
Class: |
134/7 ; 134/113;
134/12; 134/198; 134/34; 423/598 |
Current CPC
Class: |
G01N 21/65 20130101;
G01N 21/85 20130101; G01N 2021/651 20130101; G01N 2021/151
20130101; B08B 3/02 20130101; G01N 21/35 20130101; G01N 21/3577
20130101; G01N 21/15 20130101; B08B 5/02 20130101; G01N 21/359
20130101 |
Class at
Publication: |
134/007 ;
134/012; 134/034; 134/113; 134/198; 423/598 |
International
Class: |
B08B 007/00 |
Claims
What is claimed is:
1. A cleaning system for an in-process sensor comprising: a. a
sensor, wherein the sensor has a surface, which is in contact with
a process fluid; and b. a scouring jet having an inlet and an
outlet; wherein the process fluid is in contact with said inlet of
the scouring jet and, wherein the jet is positioned relative to the
sensor such that discharge from the outlet impinges on the surface
of the sensor.
2. The cleaning system of claim 1 further comprising valves.
3. The cleaning system of claim 1 wherein the sensor is an
Infrared, Raman or Near Infrared spectroscopic instrument.
4. The cleaning system of claim 3 wherein the instrument has a
probe.
5. The cleaning system of claim 4 wherein the probe has a window in
contact with the process fluid.
6. The cleaning system of claim 5 wherein the instrument is an
Infrared spectroscopic instrument.
7. A method for cleaning an in-process sensor comprising: a.
directing a portion of the process fluid to a scouring jet; and b.
discharging said fluid from the scouring jet such that the fluid
impinges on the sensor.
8. The method of claim 7 wherein the cleaning method is performed
continuously.
9. The method of claim 7 wherein the cleaning method is performed
intermittently.
10. The method of claim 7 further comprising measuring at least one
characteristic of the process fluid.
11. The method of claim 10 wherein the measurement is performed
continuously.
12. The method of claim 10 wherein the measurement is performed
intermittently.
13. The method of claim 7 further comprising measuring at least one
characteristic of a contaminant on the sensor.
14. The method of claim 13 further comprising a control strategy
for adjusting intensity, frequency and duration of cleaning.
15. The method of claim 7 further comprising treating the process
fluid prior to entering the jet.
16. The method of claim 15 wherein the treatment is heating,
cooling, vaporizing, condensing, removing particulate matter or
adding particulate matter to the process fluid.
17. The method of claim 7 used in a batch process.
18. The method of claim 7 used in a continuous process.
19. A pharmaceutical process including using the cleaning system of
claim 1.
20. A process for making or processing biological materials
including the cleaning system of claim 1.
21. A process for making titanium dioxide including the cleaning
system of claim 1 in process steps selected from the group
consisting of chlorination, oxidation, finishing, by-product
processing and precipitation.
Description
FIELD OF THE INVENTION
[0001] This invention relates to an improved system and method for
cleaning of in-process sensors.
BACKGROUND OF THE INVENTION
[0002] In-process sensors, such as on-line sensors, are used widely
in the chemical, pharmaceutical, and food processing industries to
measure one or more characteristics, such as composition,
temperature, pressure, or pH of a process fluid. All of these
sensors have a surface by which the sensor interacts with the
process fluid in order to make the desired measurement. For
example, spectroscopic instruments interact with process fluid
through some type of optical window. Normal operation of such
sensors typically requires that the surface of the sensor be
absolutely free of contaminants, such as organic growth, solids,
films or coatings, in order to take accurate measurements. For many
processes this requirement is difficult to achieve. Therefore,
various methods have been developed for cleaning the surfaces of
such sensors.
[0003] Some methods for cleaning in-process sensors require
removing the sensor from service, either by physical removal of the
sensor from the process installation or by isolating (valving off)
the sensor from the process. Both of these methods can be time
consuming, especially if the sensor surface fouls quickly. These
methods are potentially dangerous, for example, if the process
involves toxic or otherwise hazardous chemicals. These methods may
also harm the equipment. Moreover, the process itself, in addition
to the process measurement, may be suspended until after cleaning
has been completed.
[0004] An upgrade to isolation of an in-process sensor for cleaning
purposes is available in some systems, wherein a cleaning fluid is
directed at the sensor during operation. These systems are limited
to those where the process is not detrimentally affected by
addition of the cleaning fluid. One example is in waste water
treatment where clean, pressurized water and/or air is directed at
a sensor for cleaning purposes.
[0005] Mechanical methods have also been developed for cleaning of
in-process sensors. Such methods involve use of wipers, brushes,
and the like to physically scrape contaminants off the sensor.
Disadvantages of these methods include limited use with viscous
process streams, the necessity to suspend the process measurement,
and difficulty in designing a mechanical cleaning device into the
process equipment, especially for a process containing corrosive or
otherwise hazardous streams.
[0006] Ultrasound has been applied to cleaning of in-process
sensors. The use of ultrasound generates cavitation near the sensor
to remove solids. However, ultrasound is limited to use with low
solids and viscosity process streams, at pressures below 100 psig,
certain temperatures, and streams with low specific gravity.
[0007] U.S. Pat. Nos. 4,307,741 and 4,385,936 disclose an apparatus
and a process for cleaning a probe inserted into a sample process
stream. The apparatus comprises a canister containing a cleaning
agent, from which the cleaning agent is discharged, mixed with
water and pumped through a nozzle with a jet spray end directed at
the probe. The method is described as an improvement over cleaning
methods that involve (1) removal of a probe from a process, (2) use
of ultrasound to vibrate process fluid as it passes the probe and
(3) use of brushes and/or wipers while the probe is in service.
Nevertheless, the apparatus and method rely on introduction of a
material (i.e., cleaning agent) foreign to the process stream.
[0008] U.S. Pat. No. 5,185,531 provides a cleaner for an in-line
optical sensor comprising a blade. The blade mechanically wipes the
surface of a sensor window. Measurements from the sensor are
suspended until the cleaning operation is complete and data
re-stabilizes.
[0009] German Patent Application DE 35 38 313 A1 discloses a device
to clean sensors in bodies of water such as ditches around oil
storage tanks, where the sensors are contaminated with animal or
plant material. The device is essentially a hose with a nozzle from
which a pressurized fluid is discharged so as to impact the
external surface of the sensor. The pressurized fluid is water
and/or air, which generates bubbles or current in the water,
creating an oscillatory motion at the surface of the sensor to
remove contaminants.
[0010] All of the aforementioned methods include numerous
limitations and disadvantages. Therefore, it is desirable to have a
cleaning system for in-process sensors, that allow for in situ
cleaning of the sensor surface while the sensor is in operation,
that is, measurement need not be suspended during cleaning. It
would further be advantageous to clean the sensor without
introducing foreign material, such as cleaning fluids into the
process. The present invention meets these needs.
SUMMARY OF THE INVENTION
[0011] The present invention provides a cleaning system for an
in-process sensor comprising:
[0012] (a) a sensor, wherein the sensor has a surface, which is in
contact with a process fluid;
[0013] (b) a scouring jet having an inlet and an outlet;
[0014] wherein the process fluid is in contact with said inlet of
the scouring jet and, wherein the jet is positioned relative to the
sensor such that discharge from the outlet impinges on the surface
of the sensor.
[0015] The present invention further provides a method for cleaning
an in-process sensor, comprising:
[0016] (a) directing at least a portion of the process fluid to a
scouring jet; and
[0017] (b) discharging said fluid from the scouring jet such that
the fluid impinges on the sensor.
[0018] The improved cleaning system and method of the present
invention are useful in any process where there is present an
in-process sensor susceptible to contamination from the sensor's
environment, including components of the process stream. The
improved cleaning system and method are particularly useful for
processes where sensors are exposed to high solids, viscous
streams, toxic, corrosive, or otherwise hazardous streams where
removal of the sensor, or even isolating the sensor may create
dangerous conditions. Furthermore, the system and method are useful
for processes that contain highly reactive or hazardous materials,
and, where use of even relatively benign cleaning agents such as
air and/or water are not possible. In such systems, use of the
cleaning system and method are especially advantageous to provide
safe, reliable measurements for both continuous and batch
processes.
[0019] Advantages of the cleaning system and method of this
invention include:
[0020] Continuous process operation and sensor operation during
cleaning of sensor.
[0021] Use of process fluid avoids introduction of a foreign
material into the process.
[0022] Cleaning system is wholly contained within process
operations, avoiding the need to remove the sensor to clean.
[0023] Process fluid is never contaminated with non-process
cleaning fluid.
[0024] Stringent control of composition of the process fluid is
maintained.
[0025] Viscous process fluids can be used.
[0026] Improved safety of operation when process fluid comprises
hazardous (toxic, corrosive, highly reactive) materials.
[0027] Sterile conditions are maintained when sensors are used in
biological and pharmaceutical systems.
[0028] High level of control over cleaning operation is available
by independently adjusting intensity, frequency and duration of
scouring.
[0029] The improved cleaning system and method are useful in a
number of industries wherein in-process sensors are employed. A few
examples include chemical processes where the process fluid
comprises corrosive, toxic or other hazardous components (e.g.,
titanium ore chlorination), processes in the pharmaceutical and
food industries where careful control of the composition of the
process fluid is important, if not critical.
BRIEF DESCRIPTION OF THE FIGURE
[0030] FIGURE is a schematic diagram of a cleaning system of this
invention for use in a continuous process.
DETAILED DESCRIPTION
[0031] The present invention provides a system and method for
cleaning in-process sensors. The present invention is extremely
versatile, applicable in nearly all process environments where
in-process sensors are used for measurements of process conditions
and compositions. The cleaning system can be used in batch or
continuous processes. The cleaning system is not limited by
temperature, pressure, or chemical environment so long as
appropriate equipment for such condition is utilized, which can
readily be determined by those skilled in the art. Indeed, specific
advantages of the cleaning system relate to its utility in highly
corrosive environments, wherein the fluid is highly viscous and
erosive.
[0032] The cleaning system of this invention enables the removal of
contaminants, such as organic growth, solids, gels, films or
coatings comprising gaseous or liquid phases, from the surface of
an in-process sensor. An in-process sensor is defined herein as an
analytical instrument, which interacts with a process fluid,
resulting in a measurement of one or more characteristics of the
fluid and its components. Furthermore, by "in-process" it is meant
herein to encompass large manufacturing operations, such as
processing plants for commodity chemicals, as well as small scale
manufacturing operations, such as those for fine chemicals and even
laboratory scale syntheses. Examples of characteristics of a
process fluid capable of being measured include electrical
characteristics such as pH or conductivity and the concentration of
one or more chemical components of the fluid. The sensor may also
be part of a vessel through which the instrument transmits, such as
a nuclear magnetic level device. This invention is particularly
advantageous when used to clean sensors which measure
concentrations of at least one component of the process fluid.
[0033] Examples of in-process sensors suitable for use with the
cleaning system of this invention include electrodes, such as pH
meters and dissolved oxygen analyzers, membranes, nuclear density
and level gauges, and spectroscopic instruments, including
Infrared, Raman, and Near Infrared instruments and particle size
detectors. The spectroscopic instruments may use cells or probes.
The preferred sensor for any particular application will depend on
the process, that is, the equipment being used, operating
conditions (temperature, pressure), the characteristic being
measured, chemical composition, reactor vessel design, etc.
[0034] The cleaning system of this invention is particularly
advantageous when Infrared, Raman or Near Infrared spectroscopic
instruments are used for composition measurements. When such
instruments are used, probes are preferred over cells. In a
particular application, for composition measurements of a process
fluid in the chlorination of titanium ores, use of an Infrared
spectroscopic probe is preferred. More preferably, for this
application, the probe is a Fourier transform infrared probe
(FTIR), and most preferred is a FTIR attenuated total reflectance
(ATR) probe. Preferably the ATR probe has a diamond or sapphire
window exposed to the process fluid. For use with process fluids
from the chlorination of titanium ores, the preferred window is a
diamond window, which introduces less interference in the desired
spectroscopic range.
[0035] In the cleaning system of this invention, the sensor has a
surface which is in contact with a process fluid. "Surface" of the
sensor is meant herein to include windows of spectroscopic
instruments as well as windows on reaction vessels through which an
electromagnetic signal may pass to generate a measurement,
electrode surfaces, cell walls, and the like. Contact of the
process fluid with the sensor may occur by passing the fluid
through a pipe upon which the sensor, such as a spectroscopic
probe, is mounted, or by inserting the sensor, such as an
electrode, into the process fluid in a reaction vessel, for example
through a valve or flange. The sensor may contact the process fluid
through a port in a main reaction vessel, such as a stirred tank or
a pipe or continuous stirred tank reactor (CSTR) in a continuous
process. Frequently, the sensor will contact the process fluid
through a side stream from a main process fluid, for example
through a sampling system.
[0036] By "process fluid" it is meant herein the contents of a
reaction vessel. The process fluid may comprise a liquid and/or a
gas and often will contain entrained solids. In a continuous
process, the process fluid may be in the form of a process stream
flowing through a pipeline reactor or one or more of a series of
continuous stirred tank reactors. The process fluid may be in the
form of solution or slurry in a batch reaction vessel, such as a
stirred tank. In a batch process, there is further provided a pump,
which may be located within a batch reaction vessel or external to
the vessel through which to transfer process fluid to the jet.
[0037] The scouring jet of this invention is a vessel, such as a
pipe, from which a fluid is emitted wherein the fluid, upon being
emitted, expands into the environment immediately surrounding the
outlet of the jet and decelerates. The scouring jet has an inlet in
contact with the process fluid and through which the fluid enters
the jet and an outlet from which the fluid is emitted. The jet
inlet may be in contact with the process fluid directly from the
reaction vessel. More commonly, and preferably, a side stream from
the reaction vessel is used to direct a portion of the process
fluid to the jet inlet.
[0038] It should be recognized that the primary function of the
fluid directed to and emitted from the scouring jet is to clean the
sensor surface. Even though the jet directs fluid toward the
sensor, and the sensor may measure a characteristic of this fluid,
a separate flow of fluid, different from the jet flow is generally
the main source of measurement for the sensor.
[0039] The outlet of the scouring jet may be comprised of a single
nozzle or multiple nozzles from which the fluid is emitted. The jet
outlet is smaller in diameter than the vessel into which the jet
discharges the fluid. Decreasing the size (diameter) of the outlet,
results in increasing the velocity of flow from the jet. The shape
of the outlet nozzle(s) may be designed in any shape suitable to
clean the surface of the sensor. For example, a small single
optical window or electrode may be effectively cleaned by a nozzle
having a small round shape. A large optical window or membrane may
be effectively cleaned by a nozzle with a large diameter, a
slot-shaped nozzle, or even multiple small round-shaped
nozzles.
[0040] The scouring jet is positioned relative to the sensor such
that discharge of the process fluid from the jet outlet impinges on
the surface of the sensor in contact with the process fluid. The
distance of the jet outlet from the sensor depends on the
conditions into which the fluid is emitted and the geometry and
dimensions of the jet, including those of the jet outlet, angle of
emission from the jet relative to the sensor and relative to a
process flow direction, and others. Such parameters can be
optimized using standard engineering calculations. In one
particular application, that is, wherein the sensor measures
composition of a process fluid in chlorination of titanium ores,
the jet outlet is positioned between 0.25 and 1.0 inches from the
sensor surface.
[0041] The angle at which the jet flow impinges on the sensor
surface is in the range of 0.degree. to 90.degree., where 0.degree.
is parallel to the sensor surface and 90.degree. is perpendicular
to the sensor surface, preferably 45.degree. to 90.degree.. The
preferred angle and distance between the jet and the sensor may be
determined experimentally or by calculations so that for a given
geometry and velocity the desired degree of cleaning will be
achieved. Harder contaminants and smaller sensor surfaces are
better suited to impingement at higher angles, that is,
perpendicular to the sensor surface. Softer contaminants and larger
sensor surfaces may be better suited to impingement at lower
angles, that is, more parallel to the surface. When the sensor is a
flow-through spectroscopic cell, where a perpendicular jet would
interfere with the spectroscopic light beam, placing the jets at an
angle less than 90.degree. is desirable, to limit jet interference
with equipment surrounding the sensor.
[0042] It should be recognized that flow of fluid through the jet
need not be continuous. Valves may be positioned to permit or
prevent or control flow of fluid through the jet. For example, a
valve may isolate the process fluid from the sensor, if it is
desired to discontinue the measurement during the cleaning process.
Alternatively, a valve may isolate the scouring jet from the
process fluid, in order to operate the cleaning system on a less
than continuous, that is, periodic, basis. Furthermore, volumetric
flow of process fluid through the jet may be controlled by using
valves. Such valves may be operated manually or preferably,
automatically. The valves selected should provide good control of
flow and be durable. For example, for use with process fluids
comprising solid particulates, erosion resistant valves, such as
those with ceramic liners are effective.
[0043] Process equipment surrounding the sensor is preferably made
from materials that are erosion resistant. If easily abraded
materials have been used, such materials are preferably coated with
hard-facing or shielded with a hard, erosion resistant material. In
addition, the pipe or vessel into which the sensor is inserted is
preferably sufficiently large so the velocity of fluid exiting the
jet can drop rapidly after impact with the sensor in order to
minimize potential for damage to equipment surrounding the sensor
which may be impacted by the jet flow deflected after impact with
the sensor.
[0044] During operation of the cleaning system of this invention,
movement of the process fluid through the system may induce
vibration due to design of the scouring jet, sensor and process
lines through which the fluid passes. This vibration may be
detrimental to measurement accuracy. Preferably means should be
take to avoid the vibration such as, stiffening the jet, bracing
the sensor chamber and placing flow obstructions, such as valves
and elbows in the process vessels at a distance from the sensor and
jet. Preferably any obstruction is located at least 10 diameter
measures upstream and 5 or more diameters downstream of the
jet.
[0045] The method of this invention comprises directing at least a
portion of a process fluid to a scouring jet. It should be
recognized that the flow of process fluid to the jet can be
controlled independently from the flow of fluid to the sensor. The
portion of the process fluid directed to the jet can be as much as
100% of the entire process fluid flow, but preferably is less than
50%. Directing 100% of the process fluid flow to the jet may be
advantageous when the sensor surface is so contaminated that the
objective is to clean the surface until the contamination is
sufficiently reduced and/or eliminated. When a portion of the
process fluid is directed to the jet, the portion is typically
separated from the main process fluid as a side stream, especially
using sample system principles. The portion of the fluid directed
to the jet is discharged from the jet such that the fluid impinges
on the sensor surface, thereby cleaning the surface. Both the
velocity of the jet as well as any suspended solids present in the
process fluid provide scouring action to clean the sensor.
[0046] The method of this invention may be performed continuously
during operation of the sensor, or intermittently, based on a
periodic schedule, especially if the rate of fouling is well
understood, or on an as-needed basis, that is, when fouling of the
sensor is either suspected or detected. The method of this
invention may be controlled with respect to duration of the
cleaning, if cleaning is not performed continuously, as well as
with respect to intensity of the cleaning, such as due to velocity
of the fluid discharged from the jet.
[0047] The duration of a cleaning cycle, when intermittent cleaning
is practiced may be from as short as a few seconds to many hours.
The fraction of time cleaning occurs during process operation may
be less than 1% of the time to as much as 100% of the time. To
minimize potential for erosion of the sensor surface, preferably
duration of cleaning should continue only as long as necessary to
remove the contaminants.
[0048] The intensity of the process fluid exiting the jet should be
sufficient to remove the contaminants, that is, to clean the sensor
surface. However, consideration must be given to minimize damage to
the sensor and its surrounding environment. Intensity is a function
of velocity of the jet, in addition to the characteristics of the
process fluid, distance of the jet outlet from the sensor and other
factors, including, for example, hardness of particulate materials
in the process fluid.
[0049] The preferred jet velocity may range from a few inches per
second to several hundred feet per second. In operation, the
preferred velocity will depend on the composition and
characteristics of the process fluid, distance of the jet outlet
from the sensor, and other factors such as hardness of the
contaminant, durability of the sensor surface, which can be
determined by experimental optimization.
[0050] It may be desirable to treat the portion of the process
fluid from the main process fluid. Such treatment may involve, for
example, heating or cooling the process fluid, vaporizing a
condensed process fluid, or removing or adding particulate matter
to the fluid. It may be particularly desirable to remove
particulate matter that may be particularly abrasive. Particulate
matter may be removed, for example, by means such as filters,
cyclone separation. However, it should be recognized there is
reduced scouring absent particulates in the fluid.
[0051] In a preferred embodiment of this invention, the cleaning
system of this invention further comprises a control strategy. The
control strategy may provide for independent adjustment of the
intensity, frequency and duration of the cleaning operation. Thus,
a high level of control over the cleaning system is provided. The
sensor may provide a measurement of a characteristic of a
contaminant that obstructs or obscures the sensor in addition to
measuring the desired characteristic of the process fluid.
Spectroscopic probes are the preferred sensors for this mode of
operation, more preferably Infrared probes, and most preferably,
FTIR ATR probes. In one example of a control strategy, the sensor
provides a measurement of a characteristic of the contaminant,
wherein the measurement relates to the concentration of the
contaminant, and compares the measurement with a predetermined set
point. Operation of the scouring jet is modified in a manner to
maintain or reduce the concentration of solids or contaminants
below the set point.
[0052] An important advantage of this process is that the cleaning
method can be operated while the sensor continues to monitor the
process and perform the measurements. This is particularly useful
when the sensor is being used in classical continuous feedback
control operation.
[0053] The cleaning system and method of this invention has
particular utility in process operations, using in-process
spectroscopic probes, especially Infrared probes, such as the
process described in U.S. patent application, Ser. No. 09/739597,
filed Dec. 18, 2000, the teachings of which are hereby incorporated
by reference. For example, in the process for making titanium
dioxide, the present invention may be used in the chloride or the
sulfate process to control or monitor steps in the process
including controlling or monitoring in chlorination, oxidation,
finishing or in precipitation and finishing, respectively.
[0054] In addition, manufacturing processes in the pharmaceutical
and biological materials industries are particularly suitable to
include the use of the present invention. For example, the present
invention is directly applicable to these and other processes where
maintaining the integrity of the process stream is a consideration.
Integrity may be paramount for a process that cannot tolerate the
smallest contaminant or to protect operators from contact with a
process that may contain highly toxic, such as carcinogenic or
mutagenic, materials or organisms.
EXAMPLES
Example 1
[0055] The following specific example describes in detail a typical
installation and operation of the cleaning system and cleaning
method of this invention for a continuous process operation, with
reference to the Figure. The arrows within the piping in the Figure
indicate the direction of flow of the process fluid. In this
example, a scouring jet is used to clean the window of an
attenuated reflectance FTIR probe measuring impurities in a crude
titanium tetrachloride stream in accordance with CH2626.
[0056] A process fluid (1) derived from a fluid bed chlorinator,
which comprised a mixture of metal chlorides and oxychlorides and
suspended solid particles in a process to manufacture titanium
tetrachloride was fed to a reaction vessel (2). This fluid was
treated with water to passivate the aluminum chloride present (not
shown) and the treated fluid (3) was transferred using pump (4)
from vessel (2) to main process flow (6).
[0057] A portion of the treated fluid (5) was removed from the main
process flow (6). With valve (7) open, a main sample flow of
treated process fluid (8) was directed to an Infrared analyzer (9)
as a side stream. The analyzer comprised a diamond window (10)
which contacted the process fluid (8) and recorded a measurement,
which was transmitted to a feedback controller (not shown) to
control the amount of water added (not shown).
[0058] A secondary flow of treated process fluid (11) was directed
through open valve (12) to a scouring jet (13). Ceramic valves (7)
and (12) were controlled using a feedback loop to adjust flow
between main sample flow (8) and flow to scouring jet (11). Fluid
(11) exited scouring jet (13) through a nozzle (14), which was
round in shape and directed at an angle of 90.degree. and a
distance of between 0.25 and 1.0 inches toward window (10) of
analyzer (9), resulting in a scouring effect to remove solid
particulates and generating combined sample flow (15), which was
fed into reaction vessel (2).
Example 2
[0059] The following specific example describes in detail a typical
installation and operation of the cleaning system and cleaning
method of this invention for a batch process operation.
[0060] A Fourier Transform Infrared probe is placed in a recycle
loop on a stirred tank reaction vessel used in a fermentation
process where the fermentation mixture is the process fluid. A
recycle pump is used to remove fluid from the reaction vessel,
cycle through a sample system where spectroscopic measurements are
made to monitor the composition of the process fluid. A side stream
is removed from the recycle loop and is fed to a scouring jet. The
process fluid is discharged from the scouring jet with sufficient
kinetic energy, derived from the pressure and flow rate generated
by the pump, to clean the spectroscopic probe.
Example 3
[0061] The cleaning system and method of this invention can be
applied to analysis of fluid using flow-through infrared analyzer
cell. A fluid undergoes Infrared spectroscopic analysis in a
standard flow through cell. The fluid sample flows in the bottom of
the cell, and exits through the top of the cell. Windows on either
side of the cell permit the Infrared beam to enter one window, pass
through the cell and exit the opposite window to a detector. Solids
in the stream adhere to the windows requiring continuous removal to
permit accurate analysis of the fluid composition.
[0062] A pressurized stream of the fluid being analyzed is supplied
to two scouring jets entering the sample cell below each window and
oriented so that they impact the window at an angle of
approximately 45.degree.. This angle permits the jets to be
positioned outside the infrared beam path. Velocity through the
jets is controlled by manual adjustment of valves in the lines
leading to each jet. Optimum velocity is determined experimentally,
by slowly opening the valves until the solids coating the window
are removed.
Example 4
[0063] The cleaning system and method of this invention can be
applied to analysis of a liquid in a tank using a pH probe using a
single jet to clean both a glass and reference electrode. A pH
probe is inserted through a port in the side wall of an agitated
tank containing a liquid in which a batch chemical reaction is
taking place, producing gelatinous solids, which collect on the
surface of the pH probe electrodes. The solids on the electrodes
cause errors in measurements by the pH probe of the liquid in the
tank as the reaction takes place.
[0064] The glass and reference electrodes of the pH probe are both
flat surfaces and are adjacent, together covering an area of about
0.75 inches in diameter.
[0065] In order to clean the surfaces of the electrodes, liquid is
withdrawn from the tank into a centrifugal pump with a
variable-speed drive. The liquid exiting the pump flows through a
pipe passing through the same port used to insert the pH probe into
the tank. The flow exits through a scouring jet nozzle at the end
of this pipe at an angle of approximately 5.degree., that is,
nearly parallel to the electrode surfaces, and the flow impinges
upon the surfaces of the electrodes.
[0066] The speed of the pump is increased to increase scouring jet
velocity, and thus scouring intensity increases as the reaction
proceeds and the generation of solids increases. The speed
necessary to provide adequate cleaning at each phase of the
reaction is determined experimentally. Once an acceptable pump
speed profile is determined, the same profile is used for each
subsequent time this particular chemical reaction is performed in
the tank.
[0067] The Examples provided herein are illustrative and should not
be construed as limiting the scope of the invention. Variations
will be readily appreciated by those skilled in the art.
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